Intersubband hole-phonon and alloy disorder scattering in SiGe quantum wells

Using the $6\times 6\hspace{0.5em}\mathbf{k}\cdot \mathbf{p}$ method we calculate hole-phonon and alloy disorder scattering rates in SiGe quantum wells, and how these depend on the various parameters of the system. The relative importance of different branches of nonpolar optical and acoustic phonons is discussed, and a comparison is made with alloy scattering. The latter is found to be an important mechanism for intersubband hole relaxation, particularly for low-energy transitions at low temperatures, where it dominates over phonon scattering, while losing significance in the opposite case. The results are relevant for the design and operation of SiGe-based quantum cascade lasers relying on intersubband transitions in the valence band.